import java.util.Arrays;

public class MyPriorityQueue {
    public int[] elem;
    public int usedSize;
    public MyPriorityQueue() {
    }

    /**
     * 建堆的时间复杂度：
     *
     * @param array
     */
    public void createHeap(int[] array) {
          this.elem = new int[array.length];
        for (int i = 0; i < array.length; i++) {
            elem[i] = array[i];
        }
        this.usedSize = array.length ;
        int root = (usedSize-1-1)/2 ;
        for (int i = root; i >= 0; i--) {
            shiftDown(i , usedSize);
        }
    }

    /**
     *
     * @param root 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int root,int len) {
        int child = root*2 +1 ;
        while(child < len){
            if(child+1<len && elem[child] > elem[child+1]){
                child++ ;
            }
            if(elem[root] > elem[child]){
                swap(root , child);
                root = child ;
                child = root*2+1 ;
            }else{
                break ;
            }
        }

    }
    private void swap(int root , int child){
        int tmp = elem[root];
        elem[root] = elem[child];
        elem[child] = tmp ;
    }


    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
    public void push(int val) {
        if(isFull()){
            this.elem = Arrays.copyOf(elem , elem.length * 2);
        }
        elem[usedSize] = val ;
        usedSize ++ ;
        shiftUp(usedSize-1);
    }

    private void shiftUp(int child) {
        int parent = (child-1)/2 ;
        while(parent >= 0){
            if(elem[child] < elem[parent]){
                swap(parent ,child);
                child = parent;
                parent = (child-1)/2 ;
            }else{
                break ;
            }
        }

    }

    public boolean isFull() {
        return usedSize == elem.length;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */
    public void pollHeap() {
        if (isEmpty()){
            return;
        }
        swap(0 , usedSize-1);
         usedSize-- ;
        shiftDown(0 , usedSize);

    }

    public boolean isEmpty() {
        return usedSize == 0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        if(isEmpty()){
            return -1 ;
        }
        return   elem[0];
    }
    public void display(){
        for (int i = 0; i < usedSize; i++) {
            System.out.print(elem[i] + "  ");
        }
        System.out.println();
    }
    public void heapSort(){
        int len = usedSize-1 ;
        while(len > 0){
            swap(0 , len);
             shiftDown(0,len);
             len-- ;
        }
    }

}